Polysaccharide fibres

ABSTRACT

This invention relates to polysaccharide fibres having water absorption properties characterised by the incorporation within the fibres of at least one substance having anti-microbial properties, and to wound dressings formed from said fibres. The polysaccharide fibres are preferably formed from alginate or alginate containing additional polysaccharide materials to give additional absorbency (such as, for example, sodium carboymethyl cellulose). The fibres preferably contain a silver compound as an antimicrobial agent.

The present invention relates to polysaccharide fibres that are usefulparticularly, but not exclusively, in the manufacture of wounddressings.

Polysaccharides are natural polymers with hydrophilic properties thatare particularly useful for the manufacture of wound dressings. Inparticular, sodium alginate and sodium carboxymethyl cellulose, havebeen used in the wound dressing industry for manufacturing fibres, gelsand hydrocolloid dressings. For example, alginate fibres have been usedfor the manufacture of Sorbsan™ and Kaltosta™, two of the leading brandsin the alginate dressing market. Sodium carboxymethyl cellulose (CMC) isused for making Aquacel™, a hydrofibre wound dressing capable ofabsorbing wound exudate into the fibre structure, rather than holdingthe fluid in between fibres.

Fibres made from polysaccharides such as alginate are often used toproduce a nonwoven textile structure that has good absorption capacity,as well as the conformity of a textile structure. These fibrousdressings offer an ideal environment for wound healing since onabsorbing the wound exudate, the fibres turn into a moist gel byabsorbing wound exudate into the structure of the fibre, thereby turningitself into a gel.

Alginate is a natural polysaccharide existing widely in many species ofbrown seaweeds. Alginate is well known for its ability to form stablegels. On contact with divalent metal ions, typically calcium ions, watersoluble alginate solutions typically sodium alginate, reacts withcalcium ions and forms a gel. On contact with wound exudates, calciumalginate fibres exchange sodium ions in the wound exudate, wherby thecalcium ions in the fibres are replaced by sodium ions in the exudate.As a result, the fibres become a calcium/sodium alginate fibre. Sincesodium alginate is water soluble, the fibre absorbs large quantities ofexudate and forms a gel in situ on the wound surface.

PCT/GB95/02284 (Advanced Medical Solutions) discloses a method of makingfibres by co-spinning alginate with at least one water soluble organicpolymeric species. The addition of the water soluble organic polymersmakes the dressing more absorbent, thereby extending the duration of thedressing in use.

The present invention is concerned with the provision of anti-microbialproperties in polysaccharide fibres.

According to a first aspect of the present invention there is providedpolysaccharide fibres having water absorption properties characterisedby the incorporation within the fibres of at least one substance havinganti-microbial properties.

Preferably, the polysaccharide fibres are made from alginate or alginatecontaining additional polysaccharide materials to give additionalabsorbency (particularly sodium carboxymethyl cellulose). Preferably,the fibres are formed by extruding or spinning polysaccharide materialfrom a solution thereof. In particular, in the case of use of alginateand additional polysaccharide material these are preferably co-spun froman aqueous solution into a coagulation bath.

Preferably also, the (or at least one) said antimicrobial substance is asilver compound and in the case of extrusion or spinning as mentionedabove, this compound is preferably contained in the said solution. Thesilver compound(s) may be present in the fibres at concentrations ofbetween 0.1% (w/w) and 2% (w/w), and are preferably present atconcentrations of between 0.5% (w/w) and 2% (w/w). Most preferably, thesilver compound is able to leach from the fibres. This allows reductionof the bacterial load in a wound to which a dressing comprising fibresof the invention has been applied.

Thus, and in accordance with a particularly preferred embodiment of thepresent invention, AlphaSan, a silver sodium hydrogen zirconiumphosphate (from Milliken Chemical, Spartanburg, USA) is dissolved in anaqueous solution of sodium alginate and sodium carboxymethyl cellulose.AlphaSan is a ceramic, ion exchange resin, containing nominally 3.8%silver, and has proven efficacy against several types of bacteria. Thesolution can then be extruded via fine holes into a coagulation bath toform fibres. After coagulation of their extruded filament in a calciumchloride bath, the AlphaSan powders can be dispersed in the fibres togive it an anti-microbial effect.

It is known that silver compounds demonstrate good anti-microbialeffect. Silver alginate fibres can be made by ion-exchange of a calciumalginate fibre with silver nitrate. However, silver-containing alginatefibres produced in this way tend to have unfavorable physicalappearances. The alginate can be oxidised by the silver ions and thefibre turns black, making it unfavorable as a wound dressing material.

With the above mentioned preferred embodiment of the present invention,the silver ions can be bound inside water insoluble particles which aredispersed in the fibre. Oxidation of the fibre by the silver ions neednot occur and the fibre can retain its white physical appearance whilstat the same time demonstrating good anti-microbial effect.

Generally, the fibre will comprise a major proportion by weight ofalginate, e.g. 30–95%, and a minor proportion of CMC (carboxymethylcellulose). The alginate can be a grade high in manuronate content suchas Manucol DH from Kelco, although alginate high in glucuronate can alsobe used.

Fibres according to the present invention may be formed into a wounddressing. Any suitable process may be used to form such a wounddressing. Conveniently, however, nonwoven dressings may be formed bycarding the fibres to produce a web and then cross lapping the web toform a thick layer of felt, which is then needle punched to form aneedled nonwoven structure. The needled felt may then be slit to formindividual would dressings.

Thus, and in accordance with a second aspect of the present inventionthere is provided a wound dressing comprising polysaccharide fibres ashereinbefore defined.

The invention will now be illustrated in the following non-limitingExamples.

EXAMPLE 1

This example describes the production of anti-microbial alginate-CMCfibres, and the formation of a wound dressing therefrom. The fibrescomprise 84% Mid-M alginate, 15% CMC and 1% AlphaSan.

A 25 kg batch of fibres was prepared using 0.25 kg AlphaSan, 21 kgalginate and 3.75 kg CMC. These components were mixed in water andextruded via a spinneret plate with 40,000 holes, each having a holediameter of 70 μm. After being precipitated in a calcium chloride bath,the alginate in the final fibres was in the form of a mixture of calciumand sodium salt (alginate is a polymeric acid with a carboxylic acidgroup on each monomer unit).

Nonwoven wound dressings were formed from these fibres by carding andneedling. Silver was shown to be uniformly distributed in the fibres.

EXAMPLE 2

This example describes physical and performance testing of dressingsmade from the anti-microbial alginate-CMC fibres of Example 1. Thefibres were subjected to a range of different tests, these being asfollows.

Wound Model Analysis

The wound model was set up with a flow rate of 1 ml/hour using 0.86%saline solution. A saturated filter paper was placed on the wound modeland the dressing was placed on top of this. A 2 kg vented weight was puton top of the dressing and the dressing was left until failure. A timeto failure comparison was made between dressings tested on the woundmodel.

The results were as follows:

Store weight End weight (g) (g) Failure Time (hrs) 1.17 3.55 28.40 1.094.08 24.00

The dressing gelled on contact with fluid and remained gelled throughoutthe testing of the dressing. The gel was clear/white in colouration andthe silver in the dressing did not discolour the dressing in any way.The time to failure on the wound model was good for an alginatedressing.

B.P. Absorbency

The dressings were tested according to the method of the BritishPharmocopoeia to see how absorbent they were in saline solution (142 MMNa, 2.5 MM Ca). A piece of 5 cm×5 cm dressing was placed into an extrawide neck polyurethane bottle (Fisher catalogue No. BTK-460-110B), thisbeing a flat bottomed bottle with a sealing lid.

An amount of solution A (as defined in the absorbency test method foralginate wound dressings in the British Pharmcopoeia) 40 times theweight of the dressing was added to the bottle containing the sample ofdressing. The lid on the bottle was then sealed and the bottleconditioned in a 36° C. oven for 30 minutes. After this time, the lidwas removed from the bottle and the dressing was then lifted from onecorner and the solution allowed to drip for 30 seconds.

The dressing was then re-weighed and the amount of fluid absorbed per 1g of dressing calculated.

The absorbency test was repeated using deionised water and human serum.

The dressing of the invention was found to absorb an average of 20.7 gsaline solution/g dressing (n=10); an average of 23.7 g deionisedwater/g dressing (n=10); and an average of 20.8 g human serum/g dressing(n=2).

Silver Leach Analysis

Silver Leach from the dressing was analysed using the absorbency testmethod described above, with synthetic exudates being employed as thetest solution.

The samples were left for 7 days in a 36° C. incubator and after thistime they were lifted from one corner and the solution was allowed todrip for 30 seconds. The solution was analysed for silver content byatomic absorption.

The results using the 1.1 g dressing were as follows:

Sol A ppm Sol A % silver Delivered Mg of silver delivered Time fromDressing from Dressing from Dressing  0 Hours 0 0 0 30 Min 11.8 0.50230.0221  2 Days 9.3 0.3955 0.0174  7 Days 31.0 1.3181 0.0580 Human SerumHuman Serum ppm % Silver From Delivered from Mg of Silver Delivered TimeDressing Dressing from Dressing  0 Hours 0 0 0 30 Min 51.3 2.1795 0.0959 2 Days 64.5 2.7409 0.1206  7 Days 88.0 3.7409 0.1646MVTRCEN Method for MVTR

Deionised water was poured into each of the five Paddington cups leavinga gap of 5 mm from the rim of the cup. A circular disc of the materialbeing examined was placed on the centre of the top surface of thechamber ensuring wound contact surface towards the deionised water. Therubber gasket was placed around this and the flange was then clamped inplace. The Paddington cups were weighed and the weight recorded. Theywere then placed into the oven at 37 degrees centigrade with a relativehumidity value under 20% for 24 hours. After 24 hours they were removedfrom the oven and left to cool in a dessicator. They were thenreweighed. The MVTR was calculated using the following equation:

$\frac{\left( {{{weight}\mspace{14mu} 1} - {{weight}\mspace{14mu} 2}} \right)}{12.6} \times 10000$

The results were as follows:

Start Weight End Weight MVTR 137.96 125.55 9849.21 163.96 150.6110595.24Tensile Strength

The dressings were tested for their tensile properties in longitudinaland horizontal direction. They were tested dry in both directions andwhen wetted with 1 ml of saline and also with 1 ml of deionised water,the wetted dressing being left for 15 seconds to gel before commencingthe test. 10 samples were tested for each parameter giving a total of 60samples tested. The sample size was 2.5 cm width by 10 cm length.

The tensometer was set up with a 10 Newton load cell. The gauge lengthwas set at 50 mm and the crosshead speed was set at 300 mm/min.

The dressings were tested to failure. The tensile elongation [X Head]test method was opened and the following parameters were set.

(Hounsfield Tensometer)

-   Load Range: 0.1020 Kgf-   Extension Range: 500 mm-   Speed: 300 mm/min-   Sample Length: 50 mm-   Preload: 0.0000 Kgf

The results obtained were as follows:

Direction Dressing Average Standard Tested Tested Wet or Dry LoadDeviation Longitudinal Dry 0.3551 0.0455 Horizontal Dry 0.4626 0.0664Longitudinal Deionised Water 0.0675 0.0194 Horizontal Deionised Water0.1220 0.0155 Longitudinal Saline 0.1136 0.0168 Horizontal Saline 0.18270.0321Weight Per Unit Area

The weight per unit are was calculated as follows:

$\frac{10000 \times {weight}}{area} = {{weight}\mspace{14mu}{per}\mspace{14mu}{unit}\mspace{14mu}{area}}$

The weight per unit area was found to be 102.78 gm⁻².

Sodium Calcium Analysis

A weighed piece of 3″ by 3″ dressing (w1) was placed into each of threeextra wide neck polyethylene bottles (Fisher catalogue numberBTK-460-110B). The bottles are flat bottomed with a sealing lid. Anamount of solution A (as defined in the absorbency test method foralginate wound dressings in the British Pharmacopoeia) 40 times theweight of the dressing was added to each of the bottles containing the3″ by 3″ samples of dressing. The lids on the bottles were then sealedand the bottles conditioned in a 36 degree oven one for 30 minutes, onefor 24 hours and finally for 7 days. After this time the lid was removedfrom the bottle and the dressing was then lifted from one corner and thesolution allowed to drip for 60 seconds. The residue solution was thentested for its sodium and calcium contents by atomic absorption.

The results were as follows:

Time Na ppm in Solution Ca ppm in Solution 30 Mins 1719 293 24 Hours2117 403  7 Days 2283 463Gel Swelling Properties

The gel swelling properties were assessed by taking the dressing thatwas lifted from the solution in the sodium calcium analysis test methodand recording the weight as (W2).

The wet sample was then centrifuged at 3000 rpm for 10 minutes. Thesample was then removed and reweighed (W3).

The centrifuged sample was dried in a 105 degrees centigrade ovenovernight before reweighing to give (W4).

From the information gained the amount of fluid held in the fibres couldbe calculated and also the weight of the fluid held between the fibrescould be calculated.

W2–W3 is the weight of fluid held between the fibres.

W3–W4 is the weight of fluid held inside the fibres.

The results were as follows:

Duration Measurement Wt in Grams 30 Mins Wt of Fluid Between Fibres9.3152  4 Hours Wt of Fluid Between Fibres 9.7115 24 hours Wt of FluidBetween Fibres 11.0955  7 Days Wt of Fluid Between Fibres 12.8623 30Mins Wt of Fluid Held inside 1.9951 Fibres  4 Hours Wt of Fluid Heldinside 1.9939 Fibres 24 hours Wt of Fluid Held inside 2.0313 Fibres  7Days Wt of Fluid Held inside 2.0740 FibresAcidity/Alkalinity Testing

3 g of dressing being examined was weighed out. To this 30 ml of sodiumchloride and calcium chloride solution was added. (142 MM Na, 2.5 MMCa). This was left to stand for 2 hours. After 2 hours the solution wasdecanted. To 5 ml of the decanted solution 0.05 ml of Phenol Redsolution was added. The volume of 0.01 M Sodium Hydroxide VS required tochange the colour of the solution was determined. This volume was thesubtracted from the volume of Sodium Hydroxide VS required to change thecolour of the solution prepared in the same manner but without thematerial being examined. The difference should not be more than 1.0 mlto pass the B.P. Specification.

The pH was 6.65 and the acidity/alkalinity was 0.02, this being withinthe accepted limits according to the B.P. Specification.

EXAMPLE 3

This example describes the testing of the antimicrobial properties ofthe fibres of Example 2 in the form of a wound dressing, as compared tothree commercially available wound dressings comprisingnon-silver-containing fibres.

The wound dressings were tested dressings using a direct inoculationmethod. The test method was designed to determine the reduction in thenumber of bacteria for each of the alginate wound dressings. Testinginvolved inoculating samples of the alginate wound dressings with arange of bacteria, then determining the change in bioburden over a 3-dayperiod.

The anti-microbial activity of the wound dressings was tested against 10different bacteria, these being S. aureus (NCIMB 9518), S. aureus (NCTC13142), S. aureus (NCTC 13143), Pseudomonas aeruginosa (NCIMB 8626),Escherichia coli (NCIMB 8545), Proteus vulgaris (NCIMB 4175),Enterococcus faecalis (NCIMB 13280), Staphylococcus epidermidis (NCIMB12721), Steptococcus pyrogenes (NCIMB 8884), and Bacillus subtilis(NCIMB 8054).

The bacteria were grown in sterile Tryptone soya broth for 18–24 hoursat 35° C., and then subcultured onto Tryptone soya agar at 35° C. for18–24 hours. A suspension of bacteria containing approximately 1×10⁸colony forming units per ml (cfu/ml) was prepared in 10 ml phosphatebuffered saline (PBS) using a Neubauer counter. The suspension was thendiluted by adding 0.67 mls 1 to 100 mls PBS to prove a workingsuspension containing 6.67×10⁵ cfu/ml. Two 2 cm×2 cm pieces of wounddressing were placed in each of seven petri dishes. 1.5 ml of the6.67×10⁵ cfu/ml bacterial suspension was pipetted onto each sample(equivalent of 1×10⁶ cfu/dressing), the sample was turned over usingsterile forceps, and the timer started. At 0 hours, one piece of wounddressing was removed from a petri dish and placed in a stomacher bag. 50ml of neutraliser was added and the sample stomached for 30 seconds toextract the bacteria (10⁻² dilution). 100 μl of the extract from 1.4 wasthen pipetted into 10 ml neutraliser and mixed (10⁻⁴ dilution). 0.5 mlof the 10⁻⁴ dilution was pipetted into each of two labelled petridishes. Molten TSA was added to the dishes, mixed and allowed to set.

A second piece of inoculated wound dressing was also tested in thismanner.

Further duplicate pieces of inoculated wound dressing were tested after3, 6, 9, 24, 48 and 72 hours, testing both the 10⁻² and 10⁻⁴ dilutions.After initial inoculation, all 3, 6, 9, 24, 48 and 72 hours samples wereplaced and sealed in bags and incubated at 35° C.

Plates were incubated for 3 days at 35° C. then colonies counted.

The results are shown below, “Test Sample” referring to the wounddressing of the present invention, and Comparative Examples 1 to 3 beingnon-silver containing alginate dressings.

TABLE 1 Direct Inoculation of Dressings using 1.5 ml S. aureus Inoculum(Phosphate Buffered Saline) Percentage Recovery Comparative ComparativeComparative Time Interval Test Sample Example 1 Example 2 Example 3 0hour 100 100 100 100 3 hour 66.735 46.115 74.649 79.679 6 hour 45.93223.814 56.203 62.656 9 hour 23.996 7.971 42.503 58.645 24 hour  <1.03 ×10⁻³ <1.01 × 10⁻³ 0.548004 0.11854 48 hour  <1.03 × 10⁻³ <1.01 × 10⁻³<1.80 × 10⁻³ <8.91 × 10⁻⁴ 72 hour  <1.03 × 10⁻³ <1.01 × 10⁻³ <1.80 ×10⁻³ <8.91 × 10⁻⁴

TABLE 2 Direct Inoculation of Dressings using 1.5 ml MRSA 13142 Inoculum(Phosphate Buffered Saline) Percentage Recovery Comparative ComparativeComparative Time Interval Test Sample Example 1 Example 2 Example 3 0hour 100 100 100 100 3 hour 0.804386 9.642 124.1551 76.052 6 hour <8.80× 10⁻⁶ 1.089 63.519 91.760 9 hour <8.80 × 10⁻⁶ Not 50.298 59.828measured 24 hour  <8.80 × 10⁻⁶ <7.70 × 10⁻⁶ 0.0964 <8.60 × 10⁻⁶ 48 hour <8.80 × 10⁻⁶ <7.70 × 10⁻⁶ <9.90 × 10⁻⁶ <8.60 × 10⁻⁶ 72 hour  <8.80 ×10⁻⁶ <7.70 × 10⁻⁶ <9.90 × 10⁻⁶ <8.60 × 10⁻⁶

TABLE 3 Direct Inoculation of Dressings using 1.5 ml MRSA 13143 Inoculum(Phosphate Buffered Saline) Percentage Recovery Comparative ComparativeComparative Time Interval Test Sample Example 1 Example 2 Example 3 0hour 100 100 100 100 3 hour 36.044 51.927 84.346 135.2697 6 hour 7.68818.661 71.087 120.125 9 hour 0.466 5.071 48.987 71.784 24 hour  <1.85 ×10⁻⁵ <2.03 × 10⁻⁵ 2.8655 0.01558 48 hour  <1.85 × 10⁻⁵ <2.03 × 10⁻⁵<1.84 × 10⁻⁵ 2.07 × 10⁻⁵ 72 hour  <1.85 × 10⁻⁵ <2.03 × 10⁻⁵ <1.84 × 10⁻⁵2.07 × 10⁻⁵

TABLE 4 Direct Inoculation of Dressings using 1.5 ml Ps. aeruginosaInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour 0.00977 1.4085 49.0018 85.1562 6hour <3.25 × 10⁻⁵ 0.3521 9.9819 259.1146 9 hour <3.25 × 10⁻⁵ 55.111.4519 >520.8333 24 hour  <3.25 × 10⁻⁵ >352.11 0.0526 >520.8333 48 hour <3.25 × 10⁻⁵ >352.11 33.9382 >52083.33 72 hour  <3.25 × 10⁻⁵ >352.11362.9764 >52083.33

TABLE 5 Direct Inoculation of Dressings using 1.5 ml E. coli Inoculum(Phosphate Buffered Saline) Percentage Recovery Comparative ComparativeComparative Time Interval Test Sample Example 1 Example 2 Example 3 0hour 100 100 100 100 3 hour 0.004597 58.77193 114.9669 82.42812 6 hour<1.79 × 10⁻⁵ 19.73684 70.33113 82.42812 9 hour <1.79 × 10⁻⁵ 12.5 52.582878.48775 24 hour  <1.79 × 10⁻⁵ <2.19 × 10⁻⁵ 51.3907 92.43876 48 hour <1.79 × 10⁻⁵ <2.19 × 10⁻⁵ 133.1126 212.9925 72 hour  <1.79 × 10⁻⁵ <2.19× 10⁻⁵ 4.2384 21299.25

TABLE 6 Direct Inoculation of Dressings using 1.5 ml S. pyrogenesInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour <1.39 × 10⁻⁴ 13.33333 96.6101711.4035 6 hour <1.39 × 10⁻⁴ Not Not Not measured measured measured 9hour <1.39 × 10⁻⁴ Not Not Not measured measured measured 24 hour  <1.39× 10⁻⁴ <9.52 × 10⁻³ <1.69 × 10⁻² <8.77 × 10⁻³ 48 hour  <1.39 × 10⁻⁴<9.52 × 10⁻³ <1.69 × 10⁻² <8.77 × 10⁻³ 72 hour  <1.39 × 10⁻⁴ <9.52 ×10⁻³ <1.69 × 10⁻² <8.77 × 10⁻³

TABLE 7 Direct Inoculation of Dressings using 1.5 ml P. vulgarisInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour 3.9519 4.264099 72.2026744.05091 6 hour 1.9473 1.5130667 57.35398 16.3254 9 hour 0.5029 0.13755241.8719 11.28943 24 hour  <5.72 × 10⁻⁶ 0.18157 23.29346 8.35639 48 hour <5.72 × 10⁻⁶ 0.01169 5.70021 5.70021 72 hour  <1.03 × 10⁻⁶ <6.88 × 10⁻⁶1.078114 1.078114

TABLE 8 Direct Inoculation of Dressings using 1.5 ml S. epidermidisInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour 12.6990 11.66474 15.284667.76233 6 hour 11.2206 6.33449 10.6504 43.10999 9 hour 6.06520 3.051376.78861 29.70923 24 hour  <3.79 × 10⁻⁶ <3.86 × 10⁻⁶ 0.258943 0.439949 48hour  <3.79 × 10⁻⁶ <3.86 × 10⁻⁶ <4.07 × 10⁻⁶ <1.26 × 10⁻⁵ 72 hour  <3.79× 10⁻⁶ <3.86 × 10⁻⁶ <4.07 × 10⁻⁶ <1.26 × 10⁻⁵

TABLE 9 Direct Inoculation of Dressings using 1.5 ml E. faecalisInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour 63.07692 56.90608 120.77012110.23256 6 hour 44.61538 21.54696 109.10151 90.23255 9 hour 40 23.75691107.35122 117.2093 24 hour  5.507692 0.071823 121.35355 52.13270 48hour    1.02 × 10⁻⁴ <5.52 × 10⁻⁵ 76.42940 0.260465 72 hour  <5.13 × 10⁻⁵<5.52 × 10⁻⁵ 60.09335 4.65 × 10⁻⁵

TABLE 10 Direct Inoculation of Dressings using 1.5 ml B. subtilisInoculum (Phosphate Buffered Saline) Percentage Recovery ComparativeComparative Comparative Time Interval Test Sample Example 1 Example 2Example 3 0 hour 100 100 100 100 3 hour 37.168142 23.40426 14.6179437.3563 6 hour 23.00885 20.21277 14.61794 27.0115 9 hour 33.62831922.87234 14.28571 41.954 24 hour  18.106195 31.91489 18.27243 31.6092 48hour  35.840708 28.7234 22.92359 39.6552 72 hour  42.477876 45.1276612.62458 174.138

All samples were tested against the ten bacteria described above,including two strains of MRSA (S. aureus NCTC 13142 (EMRSA 15) and S.aureus NCTC 13143 (EMRSA 16). Results show for the Test Sample no EMRSA15 were detectable after 6 hours, for Comparative Example 1 andComparative Example 3 this was not the case until 24 hours andComparative Example 2 not until 48 hours. For no colonies of EMRSA 16 tobe detected in the Test Sample the time increased to 24 hours, this wasalso the case for Comparative Example 1 but for both Comparative Example2 and Comparative Example 348 hours were required for no EMRSA 16 to bedetected. The results for non-methicillin resistant S. aureus (NCIMB9518), a mirrored the results obtained for EMRSA 16.

The results for P. aeruginosa showed the Test Sample to be much moreactive against P. aeruginosa than the other three competitor dressings.Only a few P. aeruginosa colonies were detected after 3 hours for TestSample, for the three competitor dressing colonies were still detectableat 72 hours. The results show that for both Comparative Example 1 andComparative Example 2 the numbers present in the dressing begin to fallbut at 6 hours and 24 hours respectively the trend reversed and thenumbers started to increase, and by 72 hours the number ofmicroorganisms present increased to a level greater than the originalinoculum. The initial fall seen for Comparative Example 1 andComparative Example 2 is not seen in the results for Comparative Example3, these data showing that Comparative Example 3 has very littleantimicrobial effect and the numbers have increased significantly whencompared to the initial inoculum.

The results for E. coli showed no E. coli detected after 6 hrs for theTest Sample, after 24 hours for Comparative Example 1 and forComparative Example 2 and Comparative Example 3 E. coli colonies werestill detectable after 72 hours and for Comparative Example 3, as withthe P. aeruginosa results, a clear increase was noted when compared tothe inoculum.

The results for S. pyrogenes (NCIMB 8884) shown in Table 6 showed forTest Sample no Streptococcus remained after 3 hours. For the threecompetitor dressings no result is recorded at 6/9 hours. This is due tothe fact that the dilution plated (10⁻⁴) was not low enough to detectany remaining microorganisms. The most accurate result that can beobtained is that <2.5×10³ cfu/ml of S. pyrogenes remained at 6 hours,however there is still the possibility that no organisms remained at 6hours.

The results for Proteus vulgaris (NCIMB 4175) documented in table 7shows no P. vulgaris colonies detectable after 48 hours for Test Sample.The Test Sample showed the best activity against P. vulgaris as it stilldetectable in Comparative Example 1 at 48 hours and at 72 hours forComparative Example 2 and Comparative Example 3.

Test Sample and Comparative Example 1 show similar activity against S.epidermidis NCIMB 12721 (results in Table 8) with no colonies detectableat 24 hours, Comparative Example 2 and Comparative Example 3 prove to beless effective as colonies are still present at 24 hours, however nocolonies were detected at 48 hours.

Test Sample proved to be less effective against E. faecalis than many ofthe other organisms, only after 72 hours were colonies not detectable;this was also the case for Comparative Example 3. Comparative Example 1proved to be more effective than Test Sample against E. faecalis as nocolonies were detectable at 48 hours. Comparative Example 2 appeared tobe the least effective with greater than 60% of the original inoculumstill remaining at 72 hours.

Bacillus subtilis proved to be the least susceptible of all, theorganisms tested to all the dressings, however Comparative Example 2proved to have the greatest antimicrobial effect with only 12% of theoriginal inoculum remain at 72 hour. For Test Sample and ComparativeExample 1 approximately 45% of the original inoculum remained at 72hours and for Comparative Example 3 a clear increase was seen.

Generally Test Sample performed better than or equally as well as theComparative Example 1 dressing for all the microorganisms tested andboth showed a greater antimicrobial effect than both Comparative Example2 and Comparative Example 3 with the exception of Comparative Example 2against B. subtilis. The Test Sample showed the greatest antimicrobialeffect against EMRSA 15, P. aeruginosa and E. coli.

The invention is not intended to be restricted by details of the aboveExamples which are described by way of illustration only.

1. Polysaccharide fibres having water absorption properties andanti-microbial properties, said fibres comprise cospun alginate andcarboxymethyl cellulose having anti-microbial particles dispersedtherein, wherein said particles are silver sodium hydrogen zirconiumphosphate, and wherein said particles are present in a concentration ofbetween 0.1% (w/w) and 2% (w/w).
 2. Polysaccharide fibres according toclaim 1, wherein the fibres comprise a major proportion by weight ofalginate of between 30% and 95% inclusive.
 3. Polysaccharide fibresaccording to claim 1, wherein the silver sodium hydrogen zirconiumphosphate is present in the fibres at a concentration of between 0.5%(w/w) and 2% (w/w).
 4. Polysaccharide fibres according to claim 1,wherein said alginate is high in manuronate content.
 5. Polysaccharidefibres according to claim 1, wherein said alginate is high inglucuronate content.
 6. A wound dressing comprising polysaccharidefibres according to claim
 1. 7. A wound dressing according to claim 6,wherein the wound dressing is a nonwoven felt dressing.
 8. A wounddressing according to claim 7, wherein said wound dressing is formed by:(a) carding said polysaccharide fibres to produce a web; (b) crosslapping said web to form a thick layer of felt; (c) needle punching saidthick layer of felt to form a needled non-woven structure; and, (d)slitting said needled non-woven structure to form individual wounddressings.
 9. Polysaccharide fibres having water absorption propertiesand anti-microbial properties, said fibres comprise coextruded alginateand carboxymethyl cellulose having anti-microbial particles dispersedtherein, wherein said particles are silver sodium hydrogen zirconiumphosphate, and wherein said particles are present in a concentration ofbetween 0.1% (w/w) and 2% (w/w).
 10. A wound dressing comprisingpolysaccharide fibres according to claim
 9. 11. A wound dressingaccording to claim 10, wherein the wound dressing is a nonwoven feltdressing.
 12. A wound dressing according to claim 11, wherein said wounddressing is formed by: (a) carding said polysaccharide fibres to producea web; (b) cross lapping said web to form a thick layer of felt; (c)needle punching said thick layer of felt to form a needled non-wovenstructure; and, (d) slitting said needled non-woven structure to formindividual wound dressings.